Bhagavad Gita · Chapter 2: The Path of Understanding

Bhagavad Gita 2.67

indriyāṇāṃ hi caratāṃ yanmano'nuvidhīyate | tadasya harati prajñāṃ vāyurnāvamivāmbhasi ||

When the mind follows the wandering senses, it carries away one's wisdom, as wind carries off a boat on the water.

Modern context

One wandering sense is enough. When the mind trails after even a single one, judgement is carried off like a boat in the wind. It rarely takes much: one notification, one glance, one remembered slight, and an hour later we find we have drifted far from where we meant to go.